This invention relates to transformers, and more particularly to high frequency “dc-dc” transformers for power conversion and the like, though it is not limited to that application.
Ser. No. 10/904,371 teaches a coaxial push-pull transformer using modules, and in particular teaches how to arrange and dispose the modules and their termination for low parasitic inductance through field cancellation in counter-flowing currents.
U.S. Pat. No. 7,023,317 teaches a cellular transformer.
U.S. Pat. No. 4,665,357 teaches a matrix transformer, and more particularly, teaches various embodiments of variable transformers.
U.S. Pat. No. 5,093,646 teaches an arrangement of the magnetic cores of a matrix transformer for improved high frequency characteristics, and in particular, reduced leakage inductance.
U.S. Pat. No. 4,978,906 teaches a method of minimizing leakage inductance by grouping together the terminals of adjacent transformer sections and treating them as if they were from the same transformer section. This can be done only if all of the sections of a transformer are operating in the same mode.
Ser. No. 10/709,484, FIG. 9, and 60/473,075 and 60/479,706 teach turning on both switches of a synchronous rectifier to short circuit a transformer winding.
Ser. No. 10/905,668 and 60/593,110 teach a coaxial transformer module having synchronous rectifiers and an ac shorting switch across the secondary push-pull winding. The ac shorting switch may be off and the synchronous rectifiers may be operated normally, or both of the synchronous rectifiers may be turned off and the ac shorting switch may be turned on to short circuit the secondary winding.
Additional information on matrix transformers and prior art variable transformers can be found in a tutorial, “Design and Application of Matrix Transformers and Symmetrical Converters”, a seminar given by Edward Herbert at the Fifth International High Frequency Power Conversion Conference '90, in Santa Clara, Calif., May 11, 1990.